1. K. Pulliam, MS 1,2., D Followill, PhD 2., L Court, PhD 2., L Dong, PhD 3., M Gillin, PhD 2., K Prado, PhD 3., S Kry, PhD 2 1 The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, TX; 2 Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX; 3 Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD

2.  IMRT QA is a standard for routine verification of treatment plans  Numerous devices and criteria used  Absence of standard QA device or criteria  No clinical reference for QA pass/fail rates 2

3.  To review our institution’s patient-specific IMRT quality assurance (QA) results, including absolute dose and gamma analysis measurements for 13,002 treatment plans from 2005 to 2011. 3

4.  Absolute point dose made in homogenous phantom with CC04 ion chamber  +3% agreement criteria  Relative planar dose gamma analysis  90% of pixels passing a 5%/3mm criteria 4

5.  13,002 treatment plans from 2005 to 2011  13,308 point dose measurements  12,677 gamma measurements  Plans across 13 different treatment services  Breast, CNS, GU, GI, GYN, hematology, H&N, stereotactic spine, melanoma, mesothelioma, pediatric, sarcoma, and thoracic 5

6. Treatment service # of plans Mean dose difference (%) One SD (%) # of absolute dose failing plans/ (% of service) Mean gamma (%) # of gamma failures/(% of service) GU1831-0.171.211 (0.6)97.62 (0.1) THOR2951-0.531.446 (1.6)97.823 (0.8) HN3697-0.451.676 (2.1)97.733 (0.9) GYN9350.291.624 (2.6)97.68 (0.9) PEDI307-0.252.018 (5.9)97.82 (0.7) IMSSRT341-1.592.854 (15.8)97.64 (1.2) MESO522.602.611 (21.2)94.46 (11.5) Total13002-0.291.6302 (2.3)97.795 (0.7) *Not all data displayed 6

7. 7 V. 7 V. 8V. 9 V. 6

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10. 10 Film Processor Problems

11. Number of plans with absolute dose failure302 Single absolute dose failure (> ±3%) Passed with remeasurement188 Failed with remeasurement52 Multiple absolute dose failures (> ±3%) Passed with remeasurement34 Failed with remeasurement28 11

12.  Do we need the same level of QA for sites that overwhelmingly fall within tolerance (GU, GYN, etc)?  Do we need additional QA needed for sites that routinely fall outside tolerance (MESO, IMSSRT, Pedi)?  Or use site-specific criteria that allows for constant failure rate  Is gamma analysis useful for catching plans errors? 12

13.  Point dose agreement has improved with time (~1.35% to 1.1%)  Constant failure rates (~2.3%)  Substantially different rates of failure by treatment service  21.2% for Mesothelioma vs 0.6% for GU  Gamma not sensitive to dosimetric errors 13

14.  Dong L, Antolak J, Salehpour M, et al. Patient-specific point dose measurement for IMRT monitor unit verification. Int. J Radiat Oncol Biol Phys 2003;56:867-877.  Fenoglietto P, Laliberte B, Ailleres N, et al. Eight years of IMRT quality assurance with ionization chambers and film dosimetry experience of the montpellier comprehensive cancer center. Radiat Oncol 2011;6:1-11.  Low DA, Moran JM, Depsey JF, Dong L, Oldham M. Dosimetry tools and techniques for IMRT. Med Phys 2011;38:1313-1338.  Kruse JJ. On the insensitivity of single field planar dosimetry to IMRT inaccuracies. Med Phys 2011;37:2516-2524.  Nelms BE, Zhen H, Wolfgang T. Per-bam planar IMRT QA passing rates do not predict clinically relevant patient dose errors. Med Phys 2011;38:1037-1044.  Howell RM, Smith IPN, Jarrio CS. Establishing action levels for EPID-based QA for IMRT. J Appl Clin Med Phys 2008;9:16-25.  Ezzell GA, Burmeister JW, Dogan N, et al. IMRT commissioning: Multiple institution planning and dosimetry comparisons, a report from AAPM Task Group 119. Med Phys 2009:36:5359-5373. 14

15. Questions? 15

16. Treatment service Number of plans Mean dose difference (%)One SD Number of absolute dose failing plans/ (% of plans on service) Mean gamma (%) Lower 95th percentile Number of gamma failures/(% of failing on service) BRST67 0.081.61%2 (3.0)97.993.1%0 (0.0) CNS1383-0.231.43%13 (0.9)97.992.6%7 (0.6) GI803 0.451.80%33 (4.1)97.291.6%5 (0.6) GU1831-0.171.18%11 (0.6)97.692.5%2 (0.1) GYN935 0.291.61%24 (2.6)97.692.0%8 (0.9) HEM380-0.161.66%7 (1.8)97.793.2%2 (0.5) HN3697-0.451.62%76 (2.1)97.792.3%33 (0.9) IMSSRT341-1.592.79%54 (15.8)97.692.9%4 (1.2) MEL54-0.041.66%1 (1.9)97.292.1%0 (0.0) MESO52 2.602.58%11 (21.2)94.486.4%6 (11.5) PEDI307-0.252.01%18 (5.9)97.892.0%2 (0.7) SAR201 0.121.50%6 (3.0)97.491.9%3 (1.5) THOR2951-0.531.44%46 (1.6)97.892.2%23 (0.8) Total13,002-0.291.64%302 (2.3)97.792.2%95 (0.7) 16

17.  Evaluated the + % difference values that would yield the same rate of measurement failure observed in the data for each treatment site Treatment ServiceNum. Meas. Upper Tolerance (%) Lower Tolerance (%) GU18412.1-2.7 THOR29972.62.9 HN37752.8-2.9 GYN9583.0-2.9 IMSSRT3923.8-7.7 PEDI3245.1-2.9 MESO619.6-2.5 17